This invention relates generally to an apparatus, operation and method for measurement of blood pressure. In particular, this invention relates to an apparatus, operation and method for the detection, identification and characterization of sounds relating to either systemic or pulmonary blood pressure through the use of sonospectrography.
Blood pressure is the force exerted by the blood against the inner walls of blood vessels. Blood pressure determination is an important diagnostic tool. The blood vessels that comprise the vascular system can be grouped into two main divisions, a systemic circuit and a pulmonary circuit. In the systemic circuit, high blood pressure may indicate the presence of arteriosclerosis or other vascular disease, while low blood pressure may indicate shock or blood loss. Detection and measurement of elevated pulmonary blood pressure is a key diagnostic indicator for a number of pulmonary diseases, such as: cystic fibrosis, pleuresy, lung pulmonary diseases, and pulmonary impedance. Early diagnosis of these diseases greatly assists in symptom mitigation and improved patient quality of life.
The systemic circuit includes the aorta and its branches that deliver oxygenated blood to all body tissues, as well as the companion system of veins returning blood to the right atrium. Freshly oxygenated blood received by the left atrium is forced into the systemic circuit by the contraction of the left ventricle. When the left ventricle contracts, the mitral valve closes, and the only exit is through the aortic valve into the aorta.
The peripheral nature of certain systemic circuit arteries in the body extremities allows for the traditional indirect measurement of the systolic and diastolic pressures with a sphygmomanometer blood pressure cuff. While this method is effective for many patients, use of the traditional blood pressure cuff on an extremity may be contraindicated for patients suffering from any number of problems including severe extremity trauma, or burns. In patients where use of the traditional blood pressure cuff is contraindicated, there is no reliable alternative method of monitoring blood pressure. This is extremely important in trauma patients where prompt detection of blood pressure changes are needed to counteract the effects of shock or large blood loss.
The pulmonic circuit provides for blood circulation from the right ventricle through the pulmonary valve into the pulmonary artery. The pulmonary artery extends upward and posteriorly from the heart, dividing into right and left branches which serve the right and left lungs, respectively. Within the lungs the right and left branches of the pulmonary artery divide repeatedly giving rise to arterioles that continue into the capillary networks associated with the walls of the alveoli. Gas exchange occurs as the blood moves through these capillaries, so that when the blood enters the venules of the pulmonary circuit, it is well oxygenated and poor in carbon dioxide. The pulmonary venules merge forming small veins, which in turn converge forming larger veins. Four pulmonary veins return oxygenated blood to the left atrium, thereby completing the pulmonic circuit.
None of the arteries of the pulmonic system are located in extremities and therefore measurement of pulmonic system pressure with a blood pressure cuff is not possible.
At present, the only reliable method for measuring pulmonic system blood pressure is through use of an invasive blood pressure catheter that is inserted directly into the pulmonary artery. This diagnostic procedure has a substantial degree of risk and is expensive, its use is thus generally seen as an unjustified procedure in patients without other symptoms.
The physician may attempt to detect and differentiate the abnormal sounds that occur with elevated blood pressure using traditional auscultation. Closure of the aortic and pulmonary semilunar heart valves generate a sound component that is in the audio frequency range. As the systemic or pulmonic blood pressure increases, the frequency components of the related heart valve also increase. This increased frequency audio component is not present in a healthy patient. However, aural detection of this frequency increase is extremely difficult because the physician must determine the absolute frequency of the audio component of the heart valve of interest. Additionally, the sounds are very weak and heavily contaminated with noise from other patient heart sounds, other normal patient body sounds and external ambient noise in the room. Further, the audio component of the aortic and pulmonary semilunar heart valves are heavily attenuated as they pass through the patient""s chest and chest wall.
A need exists for a non-invasive, low cost and reliable means for determining systemic blood pressure in those situations where traditional means are contraindicated. A need also exists for a non-invasive, low cost and reliable means for determining pulmonary blood pressure.
As mentioned, the sounds related to systemic and pulmonary heart pressure are difficult to discern. U.S. Pat. No. 4,528,690 to Sedgwick; U.S. Pat. No. 3,790,712 to Andries; and U.S. Pat. No. 3,160,708 to Andries et al. disclose relatively simple electronic stethoscopes as methods for amplification of the sounds in an attempt to raise the sub-audible components into the audible range. However, simple amplification of the entire frequency spectrum, as disclosed, does not help in determining the absolute frequency of the heart valve sounds, or in detecting the subtle changes of this frequency that occur with changes in blood pressure.
To this end, U.S. Pat. No. 4,594,731 to Lewkowicz and U.S. Pat. No. 5,347,583 to Dieken et al. disclose various forms of selective filtering or signal processing on the audio signal in the electronic stethoscope. Lewkowicz discloses a means for shifting the entire detected spectrum of sounds upward while expanding the bandwidth so that they are more easily perceived by the listener. Dieken et al. discloses an electronic stethoscope having a greater volume of acoustic space and thereby improving low frequency response.
The electronic stethoscope provides a moderate improvement over conventional methods of auscultation. However, information remains in audio form only and is transient; the physician is unable to visualize the data and either freeze the display or focus on a particular element of the signal retrieved. To accommodate that deficiency, the technique of phonocardiography, which is the mechanical or electronic registration of heart sounds with graphic display, is used. U.S. Pat. No. 5,218,969 to Bredesen et al.; U.S. Pat. No. 5,213,108 to Bredesen et al.; U.S. Pat. No. 5,012,815 to Bennett, Jr. et al.; U.S. Pat. No. 4,967,760 to Bennett, Jr. et al.; U.S. Pat. No. 4,991,581 to Andries; and U.S. Pat. No. 4,679,570 to Lund et al. disclose phonocardiography with signal processing and visual/audio output. U.S. Pat. No. 5,301,679 to Taylor; and U.S. Pat. No. 4,792,145 to Eisenberg et al. disclose phonocardiography with signal processing and visual display.
The process of phonocardiography as commonly known in the art, acquires acoustic data through an air conduction microphone strapped to a patients chest, and provides the physician with a strip chart recording of this acoustic data. The strip chart is generally created at a rate of 100 mm/second. As this method is generally used, with the exception of the created strip chart, data is not stored. Thus, it is not possible to manipulate and/or process the data post acquisition. In addition, phonocardiography does not provide the sensitivity needed to monitor softer physiological sounds such as the closure of the semilunar valves and blood flow through the circulatory system.
As previously noted, one problem in traditional auscultation is ambient noise from the room in which the examination is occurring, which reduces the signal-to-noise ratio of the sounds of interest. U.S. Pat. No. 4,672,977 to Kroll discloses a method for automatic lung sound cancellation and provides visual and audio output. U.S. Pat. No. 5,309,922 to Schecter et al. discloses a method for cancellation of ambient noise to enhance respiratory sounds and provides visual and audio output. U.S. Pat. No. 5,492,129 to Greenberger discloses a method for reducing general ambient noise and provides audio output.
U.S. Pat. No. 5,036,857 to Semmlow et al. discloses a method of phonocardiography with piezoelectric transducer. Semmlow specifically recommends against Fast Fourier Transformation analysis of the phonocardiography data and relies on processing by other means. U.S. Pat. No. 5,109,863 to Semmlow et al.; and U.S. Pat. No. 5,035,247 issued to Heimann also disclose piezoelectric transducers.
U.S. Pat. No. 5,002,060 to Nedivi, discloses both heart and respiratory sensors, with Fast Fourier Transformation analysis. In the technique disclosed by Nedivi the sensors are not physically attached to the patient. Thus the sensors are not capable of detecting the low intensity sound of the aortic and pulmonary semilunar heart valves.
Devices currently known in the art do not provide either a means of determining systemic blood pressure where use of a blood pressure cuff is contraindicated, or a low risk, non-invasive means of determining pulmonic blood pressure. Additionally, the related art does not provide the level of aural sensitivity needed to reliably detect the sounds of the aortic and pulmonary semilunar heart valves and determine the precise frequency of these sounds.
What is needed is a safe, sensitive and noninvasive means of measuring systemic and/or pulmonic blood pressure. This is accomplished through the present invention. Through the use of sonospectrography, a procedure based on integral spectral analysis techniques, systemic pressure can be monitored in conditions where traditional auscultation is contraindicated. Additionally, sonospectrography can be used to monitor pulmonic pressure in an inexpensive, r noninvasive and low risk manner, allowing for the early detection of conditions such as cystic fibrosis, pleuresy, lung pulmonary diseases and pulmonary impedance. Sonospectrography is defined as the separation and arrangement of the frequency components of acoustic signals in terms of energy or time.
Further embodiments of the present invention provide a means of detecting physiological sounds, such as sounds emitted by the heart and other body organs as well as sounds related to the flow of blood through the circulatory system. Analysis of these sounds can be used to determine systemic and pulmonary blood pressure, monitor anesthesiology, determine cardiac output, monitor the circulation of diabetic individuals, and monitor fetal heartbeat as well as detect conditions such as aneurysms, arterial occlusions, arthritic decrepitation, phlebitis, verious thrombosis, intravascular blood clotting and carotid artery disease.
It is therefore an object of the present invention to provide an apparatus, operation and method for the detection and analysis of physiological sounds, such as sounds emitted by the heart and other body organs as well as sounds related to the flow of blood through the circulatory system.
It is a further object of the present invention to provide an apparatus, operation and method to be used to determine systemic and pulmonary blood pressure, monitor anesthesiology, determine cardiac output, monitor the circulation of diabetic individuals, and monitor fetal heartbeat as well as detect conditions such as aneurysms, arterial occlusions, arthritic decrepitation, phlebitis, venous thrombosis, intravascular clotting and carotid artery disease.
It is a further object of the present invention to provide this apparatus, operation and method through the use of sonospectrography.
It is a further object of the present invention to provide this apparatus, operation and method through a synchronized and coordinated combination of sonospectrography and electrocardiogram signals.
It is a further object of the present invention to provide this apparatus, operation and method through visual display means that provide insight to the subtle characteristics of the acoustic signature.
It is a further object of the present invention to provide this apparatus, operation and method through selective time and frequency windowing of the acoustic signals.
It is a further object of the present invention to provide this apparatus, operation and method through real-time signal processing or recorded-signal post processing.
It is a further object of the present invention to provide this apparatus, operation and method through use of single or multiple transducers.
It is a flier object of the present invention to provide this apparatus, operation and method through a computer assisted search algorithm to identify optimal placement of the transducer(s) on the patient""s chest wall.
It is a further object of the present invention to provide this apparatus, operation and method in office environments with moderate to high ambient noise levels, through adaptive noise cancellation techniques.
It is a further object of the present invention to provide this apparatus, operation and method in a form that provides for dynamic template building to facilitate disease detection and identification.
It is a further object of the present invention to provide this apparatus, operation and method through neural network techniques.
It is a further object of the present invention to provide an acoustic coupling that minimizes signal loss between the subject-detector interface and allows for the detection of sounds heretofore undetectable in a normal room environment.
It is a further object of the present invention to extend the ability of clinicians to analyze sounds which are lower in amplitude than those detectable by the unaided ear.
It is a further object of the present invention to extend the ability of clinicians to analyze sounds which are lower in frequency than those detectable by typical auscultation techniques.
It is a further object of the present invention to increase detection of a specified frequency range through the use of a tailored bandpass amplifier.
It is a further object of the present invention to provide a means for data storage, data manipulation and data transmission.
It is a further object of the present invention to provide this apparatus, operation and method through advanced processing of acoustic signatures in the time and frequency domain to isolate and display the sound components associated with pulmonary and/or aortic heart valve closure.
It is a further object of the present invention to provide an apparatus, operation and method that is suitable for routine physical examination screening and early diagnosis of elevated pulmonic blood pressure thereby providing an opportunity for early intervention to enhance the patient""s productive life.
It is a further object of the present invention to provide an apparatus, operation and method that is suitable for monitoring of systemic blood pressure in patients where use of a traditional blood pressure cuff is contraindicated.
These and other objects of the present invention will become obvious to those skilled in the art upon review of the following disclosure.
An apparatus for determining blood pressure in accordance with the present invention includes a sensor assembly comprising a housing, an electronic module, a shock dampener, a mounting means, a piezoelectric transducer, an acoustic coupling and a back cover. The sensor assembly is connected to a data acquisition module which in turn is connected to a signal processing means. The signal processing means is connected to an electronic storage means, a hard copy reproduction means, a remote connection means and a monitor. In an alternative embodiment of the invention a plurality of sensor assemblies are connected to the data acquisition module. In another alternative embodiment of the invention a means for determining an electrocardiogram is connected to the signal processing means. In yet another alternative embodiment of the invention, data acquisition module is connected to high-fidelity earphones.
The operation for determining blood pressure in accordance with the present invention includes:
1) performing start-up procedures;
2) acquiring physiologic signals;
3) acquiring ambient or background signals;
4) processing and subtracting ambient signals from physiologic signals;
5) conditioning and processing resultant data;
6) subjecting the conditioned and processed data to Fast Fourier Transformation;
7) passing the time domain components of the data through a time domain correlator and feature extraction process;
8) passing the frequency domain components of the data through a frequency domain correlator and feature extraction process;
9) comparing the time domain output and the frequency domain output to a reference pattern and feature library;
10) determining whether the time domain output and frequency domain output match known disease modalities;
11) determining whether a disease modality is indicated;
12) updating the reference pattern and feature library; and
13) providing the information regarding the disease modality to the physician so that a treatment regimen may commence.
The method for determining blood pressure in accordance with the present invention includes monitoring the sounds of the aortic and/or the pulmonary semilunar valves. Where one wishes to determine systemic pressure, the aortic semilunar valve is monitored. This is done by placing the acoustic coupling of the sensor assembly adjacent to the patient""s skin at the traditional auscultation point for the aortic valve. Where one wishes to monitor pulmonary pressure, the pulmonary semilunar valve is monitored. This is done by placing the acoustic coupling of the sensor assembly in contact with the patient""s skin at the traditional auscultation point for the pulmonic valve. Detected signals are manipulated in the same fashion noted in the xe2x80x9coperationxe2x80x9d of the present invention. The signals may be viewed and analyzed by medical personnel at any number of points during this data manipulation process to allow for the implementation of a treatment regimen. Where the sound emitted by either semilunar valve is of a higher than normal frequency, this is indicative of increased blood pressure in the corresponding circuit; that is, an increased frequency emitted by the aortic semilunar valve is indicative of higher than normal systemic blood pressure, while an increased frequency being emitted by the pulmonary semilunar valve is indicative of higher than normal pulmonary blood pressure.